I don't know about PHP, but at work our artifacts are signed, and you certainly cannot have the signing certificate on your laptop. It's stored in some secure server, and only accessible from some allowlisted build nodes, for specific builds (release branch, ...).

Now of course, there are ways around that if required, but they are, by design, manual, cumbersome and slow. I could not create a release build locally in a few minutes. A few hours maybe if the whole organisation dedicated itself to it.